Many systems utilize sensors to monitor and/or control the operation of the systems. Applications in which sensors are utilized include, for example, automobiles, machines, aerospace, medicine, industry, robotics, and the like. The sensors can be used to measure one or more system variables such as pressure, temperature, speed, acceleration, motion, proximity, and so forth. Sensor outputs may then be used as feedback in a closed-loop operation to ensure that the system is being operated at the desired conditions, that safety bounds are being observed, and that system performance is being optimized. Technological advances have enabled many more sensors to be manufactured on a microscopic scale using microelectromechanical systems (MEMS) technology. MEMS technology combines microelectronics with miniaturized mechanical systems such as valves, gears, and any other component or components on a semiconductor chip using nanotechnology. Such microsensors can operate at significantly higher speeds and with greater sensitivity as compared to macroscopic designs.
Although sensors are typically designed to be robust, sensor failure can still occur. The possibility of sensor failure is typically addressed through the use of redundant sensors. By duplicating sensor components, if a fault arises in one of the sensors, its presence is indicated by virtue of the two sensor signals being dissimilar. For example, in one prior art design, a dual sensor system utilizes at least two discrete sensor circuits, each of the sensor circuits including a sensor, an analog-to-digital converter (ADC), a processor, an output circuit and an output switch. In such a design, only one sensor generates an output signal, whereas the other sensor is used for comparison to detect faults. The dissimilarity, or mismatch, between the two sensors can be detected in real time. The implementation of such a dual sensor system is undesirably complex and large, especially when implemented within the area constraints of MEMS architecture. A complex and large structure drives up costs and/or reduces yield.
Another dual sensor design has one signal conditioning and ADC path that is used sequentially with each of the two sensors in order to generate a signal and measure the dissimilarity. The dissimilarity between the two sensors is detected with some delay. Consequently, this dual sensor design cannot detect faults in real time. Moreover, in many designs, resolution of the sensor is sacrificed in order to meet size, cost, and complexity constraints. Thus, what is needed is a dual sensor system that enables detection of sensor faults in real time and provides a high resolution output signal in a minimally sized, low cost, and readily implemented package.